mutative/src/unsafe.ts

A JavaScript library for efficient immutable updates

import { Options } from './interface';
import { isDraftable } from './utils';

let readable = false;

export const checkReadable = (
  value: any,
  options: Options<any, any>,
  ignoreCheckDraftable = false
) => {
  if (
    typeof value === 'object' &&
    value !== null &&
    (!isDraftable(value, options) || ignoreCheckDraftable) &&
    !readable
  ) {
    throw new Error(
      `Strict mode: Mutable data cannot be accessed directly, please use 'unsafe(callback)' wrap.`
    );
  }
};

/**
 * `unsafe(callback)` to access mutable data directly in strict mode.
 *
 * ## Example
 *
 * ```ts
 * import { create, unsafe } from '../index';
 *
 * class Foobar {
 *   bar = 1;
 * }
 *
 * const baseState = { foobar: new Foobar() };
 * const state = create(
 *   baseState,
 *   (draft) => {
 *    unsafe(() => {
 *      draft.foobar.bar = 2;
 *    });
 *   },
 *   {
 *     strict: true,
 *   }
 * );
 *
 * expect(state).toBe(baseState);
 * expect(state.foobar).toBe(baseState.foobar);
 * expect(state.foobar.bar).toBe(2);
 * ```
 */
export function unsafe<T>(callback: () => T): T {
  readable = true;
  let result: T;
  try {
    result = callback();
  } finally {
    readable = false;
  }
  return result;
}